The Chief Inspector of prisons Nick Hardwick has issued a stark warning on the state of prisons in Wales and England.
It comes after the UK Government admitted more prisoners would have to share cells to cope with an unexpected rise in numbers.
Mr Hardwick said cuts had left the prison system so stretched that more inmates were killing themselves, or getting deliberately sent to punishment blocks to escape crowded conditions.
Justice Secretary Chris Grayling rejected the criticisms, insisting the number of assaults and cases of self-harm were falling, and that 2,000 extra prison places were being built.
Swansea is currently the most overcrowded prison in the UK.
According to the latest figures it currently holds 455 inmates, 184% more than it's uncrowded capacity of 242.
There are currently 49 criminals serving whole life terms in English prisons, and David Cameron has vowed to ensure that "life means life" for the worst offences.
Those serving full life terms include Jamie Reynolds, who pleaded guilty to the murder of Shropshire teenager Georgia Williams last year.
Mark Bridger, who was jailed for killing five-year-old April Jones, is also serving a whole life sentence.
David Cameron has promised to ensure murderers can be kept in jail for life amid suggestions that the Government could introduce 100-year-sentences.
The Prime Minister's comments follow a long-running confrontation with the European Court of Human Rights, which has declared life sentences in England illegal because they offer no "right to review".
Ministers believe they can sidestep the ruling by letting judges sentence for hundreds of years, the Telegraph has reported.
Liberal Democrat AM Aled Roberts has welcomed the announcement of a 'super-prison' for North Wales, saying the project could create over a thousand jobs.